The present invention is directed towards a heat recovery anti-icing system and more particularly to an anti-icing system which maintains the temperature of air in the inlet filter compartment of a combustion or gas turbine power generating system at an elevated level.
Anti-icing systems of the foregoing type are well known. Such systems fall into three primary categories: compressor bleed systems, exhaust recirculation systems and heat exchanger systems. Compressor bleed systems utilize a small percentage of compressor discharge air (typically 500.degree. to 800.degree. F.) for direct-mix heating with the cold air located in the inlet filter compartment. While such a system is relatively inexpensive to construct, it exhibits significantly lower performance characteristics at moderately cold temperature (0.degree. F. to 40.degree. F.) than other systems.
Exhaust gas recirculation systems utilize a portion of the hot exhaust air from the turbine for direct-mix heating with the cold air located in the inlet filter compartment. The primary drawback of this system is that the recirculated gas contains moisture which is reintroduced into the air flow system. As a result of this moisture, it is necessary to operate the exhaust gas recirculation system in a full heating mode wherein the inlet air is heated to a fixed temperature above freezing.
Heat exchanger systems utilize exhaust gas from the turbine to indirectly heat the air being applied to the turbine compressor using a heat exchanger. Since no additional moisture is introduced into the air flowing into the compressor, the system may be operated in a limited heating mode wherein the air in the inlet filter compartment is heated by a limited temperature increment.
In prior art heat exchanger systems, the heat exchanger is located between the inlet filter compartment and the compressor. Hot exhaust gases located in the exhaust stack are applied to the heat exchanger via a control valve for indirect heating of the air flowing into the compressor. While such a system has been generally satisfactory, it exhibits several drawbacks. For example, the heat exchanger is located some distance from the exhaust stack and therefore, the exhaust gases leaving the heat exchanger are relatively cool and cause condensation of both water and sulfuric acid. Additionally, the pressure losses at both the exhaust and the inlet are relatively high.